1) Field of the Invention
The present invention relates to a storage apparatus that includes a primary storage that stores in a predetermined storage area data received from a host computer and a secondary storage that stores in a predetermined area the data stored in the predetermined storage area in the primary storage, and that reads and sends to the host computer the requested data, upon receiving a read request to read the data stored in the secondary storage area from the host computer, as well as a storage control method and a storage control program that control the storage of the data in the storage apparatus. More particularly, the present invention relates to a storage apparatus, a storage control method, and a storage control program that enable easy and efficient management of various data stored in virtual storage areas.
2) Description of the Related Art
Hierarchical storage apparatuses have been used conventionally which involves storing data that is frequently referred by a host computer on a hard disk and data that is referred not very frequently on an optical disk or a magnetic tape.
A hard disk allows fast access to stored data and an optical disk or a magnetic tape allows large volumes of data to be stored. The advantages of the hard disk and the optical disk/magnetic tape are clubbed in the hierarchical storage apparatus which allows large volume of data to be accessed fast.
Upon receiving a read request from the host computer for the data stored on the optical disk/magnetic tape, the hierarchical storage apparatus reads the requested data from the optical disk/magnetic tape and stores it on the hard disk. The host computer then refers to the data stored on the hard disk.
Thus, to store data or read data, the host computer only needs to access the hard disk, obviating the need for the host computer to recognize the optical disk or the magnetic tape. Basically, the host computer uses the hard disk as a high-volume storage medium.
Japanese Patent Laid-Open Publication No. 2000-163298 and Japanese Patent Laid-Open Publication No. H9-6541 disclose hierarchical storage apparatuses in which the storage area of the hard disk and the storage area of the optical disk together form a logical drive, which the host computer recognizes as a single virtual storage area.
However, in the conventional hierarchical storage apparatus disclosed in the above literatures, the diverse data stored in the virtual storage area may get mixed up, making data management very difficult.
To be specific, when used by a plurality of users, the diverse data of the users may get mixed up, causing accidental deletion or overwriting of data of one user by another user. The large storage capacity of the virtual storage area further compounds the problem of data management.
Thus, it is vital to have a system in place by which the diverse data stored in the virtual storage area of the hierarchical storage apparatus can be easily and efficiently managed.